Industry often has requirements to operate rotating equipment from a source of hydraulic fluid under pressure. Examples of such equipment are pumps, compressors, generators, and heavy road building machines. These devices employ a gasoline, diesel, or electric motor as a source of power, connected to a pump to drive a hydraulic motor which in turn operates the machinery. The machinery can only be operated while the source motor/pump is running. When the source motor/pump is shut off or malfunctioning, the machinery is inoperable.
Hydraulic engines with built in pumps and having tandem pistons are known and, heretofore, have been configured in different ways. Some examples of piston engines with pumps in the prior art are seen in the following U.S. patents:
Jensen, U.S. Pat No. 4,234,295, shows a dual in-line piston device operating within a well. A continuously driven hydraulic pump conveys fluid from a large cylinder, through a valve set to a first position, into a high-pressure accumulator. In the second valve position, fluid flows from the accumulator to the pump to the large cylinder, forcing a large piston upward. A small piston connected in tandem then raises well liquid to the surface.
Jensen, U.S. Pat No. 4,234,294, shows another dual in-line piston device operating within a well. A continuously driven hydraulic pump conveys fluid from a tank, through a valve set to a first position, to a large piston, driving it downward while forcing well liquid upward to storage, and charging a high-pressure accumulator with fluid through a free-piston device. In the second valve position, fluid flows from the accumulator to the pump to the free-piston device, forcing well liquid into the large cylinder, forcing the large piston upward, which returns fluid to the tank. The small piston is used to draw well liquid in to recharge the large cylinder.
In each Jensen patent, the system functions only while the motor-driven pump is running. The accumulator is used for temporary fluid storage during half of each cycle to provide a boost during the other half cycle. The purpose of these inventions is not to produce power from a rotating shaft, but to raise liquid from a well.
Chenault, U.S. Pat. No. 3,374,746, discloses a subsurface triple in-line piston device for pumping well liquid. A surface motor driven pump acts upon a first drive piston. A second piston is used for recirculating fluid. A third piston pumps well liquid to the surface. Here again, the system functions only while the motor-driven pump is running. There is no accumulator or control valve.
Shaddock, U.S. Pat. No. 3,700,360, illustrates a dual in-line piston device. High pressure fluid from a vehicle engine-driven pump is directed through a control valve actuated by a pilot valve, alternately to both sides of a drive piston. A tandem pump piston forces water at high pressure through a hose and nozzle. The device is solely for pumping water. No output shaft or accumulator is provided.
Vick, U.S. Pat. No. 5,484,269, shows a fluid intensifier having tandem pistons, a control valve and a pilot valve. The device converts high fluid flow at low pressure to low flow at high pressure. There is no output shaft or accumulator.
Whitehead, U.S. Pat. No. 5,616,005, discloses a bi-directional dual piston pump driven by fluid to pump an external fluid. A pair of control valves regulate the drive portion. No output shaft or accumulator is disclosed.
While the above-described inventions serve to pump fluids satisfactorily, none are capable of producing rotary shaft power output. Furthermore, none are able to operate for extended periods of time on a source of stored energy.
Accordingly, there is a need to provide a hydraulic engine capable of producing rotary shaft output, and operating from a source of stored pressurized fluid for long periods of time without any external energy input. Such a device would be especially useful during periods of power blackout.